1. Field of the Invention
The present invention relates to a signal receiving apparatus. More particularly, the present invention relates to an adaptive equalizer with digital eye-opening monitor unit in a signal receiving apparatus and the method thereof.
2. Description of Related Art
Digital and portable products have been continuously leading the market since the birth of digital technology, and various key technologies have been highly integrated with applications so as to provide high-speed, simple, and personalized products. Along with the increase in the speed of cable signal transmission, product designers will be confronted with more challenges in signal integrity and bandwidth adequacy of transmission media. Generally speaking, when the transmission media bandwidth is not adequate, high-speed signal will be attenuated more so that the eye diagram will not be ideal, accordingly bit error will be caused.
To transmit signal with higher speed in a particular transmission media such as RG-58 coaxial cable, conventionally the attenuated high-frequency signal is compensated so that signal with higher speed can be transmitted without producing any bit error, and this is the function performed by an equalizer. The equalizer can be disposed at the sender end or at the receiver end. However, the equalizer disposed at the sender end cannot directly detect the frequency response of the transmission media, thus the parameters thereof have to be determined by the user instead of being adjusted adaptively, except the receiver sends the detected signal back to the sender. Since the signal is transmitted to the receiver through the transmission media, the frequency response of the transmission media can be obtained by merely detecting the eye diagram of the signal so that the equalizer at the receiver end can adjust adaptively.
Regarding eye-opening monitoring, conventionally the eye diagram of a differential signal is measured. The quality of the transmitted signal and the signal timing shifting are determined by quantifying and analyzing the eye diagram.
FIG. 1 is a schematic block diagram of a conventional receiving apparatus with eye-opening monitoring function. The conventional eye-opening monitor 110 includes comparators 111, 112, and a phase interpolator 113. The eye-opening monitoring method is to detect the height of the eye diagram with the comparators 111 and 112, and detect the width of the eye diagram with the phase interpolator, so as to obtain the actual size of the eye diagram. Then, the parameters of the equalizer 120 are adjusted according to different requirement, so as to improve the quality of the received signal. Please refer to U.S. Pat. No. 6,784,653B2 and “A 10-Gb/s Two-Dimensional Eye-Opening Monitor in 0.13-μm Standard CMOS” in pages 2689-2699 of the IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 40, NO. 12, DECEMBER 2005 for the detailed information of related technology.
However, since comparators and phase interpolator are required for eye-opening monitoring in conventional eye-opening monitor, the area of the chip and the power consumption thereof are increased. The foregoing disadvantages become more serious along with the increase of operation frequency.